The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The noise a jet engine makes when it is installed under the wing of an airplane can be broken down into components. Two of the most significant components are jet noise and jet installation noise. Jet noise is the noise the jet makes and that it would make whether or not it is installed on an aircraft. Jet installation noise is the additional noise the jet makes due to the presence of the wing and flap system of the aircraft. Jet installation noise is a significant consideration for present day commercial passenger transport and freighter jet aircraft when the engines are installed under the wings.
At the present time, with new aircraft development, jet installation noise may limit or influence a wide variety of component design factors. Components that might be design influenced or limited in some manner because of the expected or anticipated influence of jet installation noise may involve one or more of the following:                restricting fan diameter;        lengthening landing gear;        increasing wing dihedral angle;        decreasing flap angle, which produces reduced low speed aerodynamic performance;        impacts to wing trailing edge design;        longer and heavier engine strut; and        affecting aircraft balance and loading.        
The use of chevron type nozzles is currently the principally accepted way of achieving jet noise reduction on an existing jet engine without a significantly large weight and performance penalty. Chevron nozzles are triangular shaped devices installed on the downstream edge of the jet engine fan and primary exhaust nozzles. The chevrons increase mixing of the flow leaving the nozzle with ambient air and reduce jet noise. In addition recent work has also shown that the chevrons can reduce jet installation noise as well, which is a major component of aircraft noise. Typical chevron design reduces low frequency noise but can in some instances produce some increase in high frequency noise. This increase in high frequency noise is typically in the forward radiation angles (as measured from the engine inlet axis, or forwardly toward the nose of the aircraft).
Thus, it would be highly beneficial and desirable to provide a jet nozzle that operates to reduce jet installation noise, as well as to inhibit the radiation of high frequency jet installation noise that is generated close to the downstream exit of the nozzle that would ordinarily tend to propagate forwardly toward the nose of an aircraft.